Optical glass with anomalous partial dispersion



e. WEISSENBERG ET AL 2,996,390

OPTICAL GLASS WITH ANOMALOUS PARTIAL DISPERSION 3 Sheets-Sheet 1 8 m w o m m m N! m min.

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Aug. 15, 1961 Filed NOV. 13, 1953 INVENTORJ 2,996,390 OPTICAL GLASS WITH ANOMALOUS PARTIAL DISPERSION Filed Nov. 15, 1953 Aug. 15, 1961 G. WEISSENBERG ETAL 3 Sheets-Sheet 2 \m im a 335m omm oom

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ommv lm ENToRs Aug. 15, 1961 G. WEISSENBERG ETAL 2,996,390

OPTICAL GLASS WITH ANOMALOUS PARTIAL DISPERSION Filed Nov. 13, 1953 5 Sheets-Sheet 3 United States PatentO Il s-1E3 of optical glasses hitherto known are plotted as abscissa and their partial dispersion values Patented Aug. 15, 1961 "ice 2 with anomalous partial dispersions. These glasses have the characteristic that they consist essentially of phosphates of the elements of the second group of the periodic system with the exception of radium, namely, phos- 5 phates of magnesium, calcium, strontium, barium.

are plotted as ordinates, the resulting functionsulievoni f a straight line. Actually the function of the highly refracting flint glasses with lower 1: values deviates upwardly in an are from the straight line.

gprovement in the correction may be obtained by using flint and crown glasses of the same refractive index but \with u values differing as widely as possible, whereby (chromatic aberrations of the second order could still not quite be taken care of. This is, however, possible if one is able to use glasses with partial dispersionvalues, 2

as nearly equal as possible and with v values as far apart as possible if at the same time the requirements relative -;tion of their refractive index n, to their v value; 'irn The crown glasses of our invention with a positive deviation Au from the straight line relations of optical glasses consist of at least percent by weight of a metaphosphate of the alkaline earth metals and at most of 50 percent by'weight of compounds of the group of oxides, carbonates and sulphates of the group consisting of the alkali and alkaline earth metals. Further, lead oxide or lead phosphate may be added to these mixes. More over, boric acid may be used as an additive.

The flint glasses with a negative deviation Au consis of to 'percent by weight-of-leadorthophosphate whereby it is to be noted that the lead orthophosphate is to be brought into the glass melt as an already prepared compound to which is to be added up to 15 percent by weight of metaphos phates of the second group of the periodic system and oxides of tungsten and tantalum. Ofspecial advantage is an addition up to- 8 percent by weight of oxides or carbonates 'of'the alkali imetals. "The flint glasses with apositive deviation Au and extremely low index ofrefraction consist of a, glass forming substance preferably of aphosphate of the alkali metals, the alkaline earth metals or both and titanium dioxide.

A number of glasses of. the invention are illustrated by way of example in the following tables. in which the deviation, -Au, of the-.glassescfrom thenvra. straight line inclination are given in v values and the displacement towards the right from the straight line for the crown glasses and the displacement towards the left or towards the right for the flint glasses are indicated for each glass with the plus or minus sign.- The examples given are by way of illustration and not of limitation.

to the refractive indexes are preserved or adhered to.

It is of the greatest advantage at the same time when the flint glass deviates to the negative side aud t-he crown glass to the positive side of the 11-2 line, that is-,--that-the flint glass has a 9 value corresponding to a smaller v value and the crown glass a 5 value corresponding to a large 11 value. It can also be of advantage to combine flint glasses with high and with low indexes of refraction if at the same time the partial dispersions deviate re spectively to the negative and to the positive sides of the straight line function of the optical glasses hereto'fbie known in the 11-9 diagram.

Our present invention relates to glasses of this..type

The deviations of the glasses of the several tables from the straight line functions of the optical glasses heretofore known are shown graphically in the accompanying drawings in which the several examples are identified by a reference letter given in the respective tables and in wh h;

FIG. 1 is a graph illustrating the deviation of the several glasses of tables 1 to 7, inclusive,

FIG. 2 is a graph illustrating the deviations of the several glasses of tables 8 and 9, and,

FIG. 3 is a' graph illustrating the deviations for the several glasses of'tables 10 and 11.

In FIG. 2 the function of the optical glasses heretofore known bends upwardly beginning at'a vvalu'e of 35 as indicated by the broken line.

(In percent by weight) Melt N0. Identity .MgCP 03): L Os BzOg nn H 0 Av letter a 97. 4 2. 6 67. 8 0. 532 +1. 9 b 95. 3 4. 7 68:0 0. 538 +5. 7 c 91. 0 9. 0 68. 1 0. 536 +4. 5 d 83, 4 16. 6 67. 6 0. 534 +3. 1 e 77. 0 23. 0 67. 0 0. 534 +3. 4 f 71. 5 28. 5 67. 2 0. 537 +4. 5 a 76. 0 l2. 6 69. 8 0. 535 +6. 5 h 64. 5 25. 8 68. 5 0- 532 +2. 6 z 60. 6 30. 3 68. 1 '0. 533 +2. 2 I: 67. 2 34. 4 67; 2 0. 634 +2. 4

melt of magnesium Table 2 V (Showing a melt of magnesium metaphosphate and sodium sulphate in percent by weight) Table 3 (In percent bywaight) [Showing as magnesium anetaphosphate and vcalcium oxide system, namely izummesium Identity Mg(POa)2 NazSO4 letter calcium oxide and boric oxide and also a final Melt No.

metaphosphate metaphosphatg and calcium fluoride] 22 v in I. A a t a h m 6 0 0 i 45 3106 V $06 1 i 00 7 m m w. v 1232 20 32 m i f 3 2 1 i A w i m V m 5%. 1337 1 W V ama mm i m .m w D D O .O QO O 664 2 03 6 an? m 3 p m P r 31774 30 m .0 0 0 0 0 0 X 8 00 M -v 0. m H a 7 7 &&&&Z o o h a 0 h h v 267845 .1. 39668 1. 25 H. 9 0 17179 f. h v h m m W um m w m m m 1111111 8 9 1 t P t d 1 l 6 2 W 0 H i a n m ma m o m um w w 1 l w m 0 b e b w e D 5555 h 0 n 5 t a n 45 m. n LLLLL m m LL m 6 T m a \m Q2 3 V a i v 2. 0 4 w m 5 w e 6 w m 4 V & w. m. N m b 3 80654 .M .W m 62 k .W m 0 1 n w t e O 11&74 b t P 0 i9 b t a Q a m M w m 0 1222 a m m b a m a O T c. a T h P T m P M m w B m. w. w m .m \n m t i a m m x 3 mm M 3 m h 4 m o m a 4 a &9 25 V a 5 i w s 3 i P W m s luayxv m m 9% p m 8 H mm 7 I P .m 8 m 7 h M b a m H a g t vw mu m m m mu m mm mm m mm m 3 8 mm m m1 2 mm m M tuow: w M v: 8 m .0 n In I mflofiqfl m 8 4 I h a r m 3 o u m o Iain M I & n .N h N I t N .R t t R h R 5 W W .& m .m M 8 m S M 8. mm? m M mm? m w M w 32323. mnwmw vi a M v 2w Table 8 (In percent by weight) {In this table there is shown first a glass of magnesium metaphosphate and lead orthophosphate, then glasses of magnesium metaphosphate, lead orthophosphate and tungstic oxide, and finally of lead orthophosphate, tungstic oxide and phosphorus pentoxide namely magnesium metaphosphate, lead orthophosphate, tuugstic oxide and lithium carbonate] Melt N R 280 R 341 R 343 R 351 R 350 R 432 Identity letter a b c d e MgCPOa): 11 10.8 10.4 10. 4 6.7 3.4 87.0 83 3 83. 3 86. 2 83. 7 2. 2 6 3 10.0 10.4 4.2 1.

Table. 9

(In percent by welght) [In this table are shown combinations of magnesium metaphosphate, lead orthophosphate and tantalic oxide] Identify- Melt N0. ing Mg(POa)z Pb3(PO4)2 T8105 75, v 0 Av letter (I 10. 8 87. 0 2. 2 1. 8183 30. 1 584 6. O h 10.6 85. 1 4. 3 1. 8324 29. 7 588 4. 2 i 10. 3 83.3 6. 4 1. 8167 29. 8 589 3. 5 I: 10.2 81.6 8.2 1.8287 29.1 591 3 0 Table 10 (In percent by weight) [In this table are shown glasses in which sodium carbonate and titanium dioxide are used in addition to the glass forming substance, magnesium metaphosphate, the melt being held at the melting temperature until the sodium carbonate has been completely decomposed and the carbon dioxide driven ofi] Identi- Melt N0. Mg(PO3)1 N11200: T102 11 v 19 Av tying letter R 439--- 54. 0 43. 3 2. 7 1. 5237 54. 5 561 +5. 5 l R 440- 52. 6 42. 1 5. 3 1. 5431 47. 3 574 +6. 0 m R 441 51. 3 41. 0 7. 7 1. 5620 42. 6 585 +7. 5 n W 563/77 324. 40 10 1. 5782 39. 6 590 +6. 7 o R 4 48. 7 39. 1 12. 2 1. 5943 37. 0 594 +5. 5 p R 443----- 47.6 38. 1 14.3 1. 6065 35. 8 596 +5. 0 9

Table 11 (In percent by weight) [In this table are shown further melts which have been formed from sodium yrophosphate. The cryolite (Na AlFo) used in these melts serves only as a flux] Identi- Melt No. NaPO; Nalmm NaaAlFe T10, 11,, v 0 Au t in letter R 45.5 40.9 4.5 9.1 1.5472 38.3 597 +7.7 r P. 40.8 44.9 4.1 10.2 1.5534 37.5 502 8.5 a R 42.5 42.5 4.2 10.5 1.5570 35.7 503 +8.1 t w 44.4 40.0 4.5 11.1 1. 5597 35.1 507 +8.8 71. R 38.5 45.1 3.8 11.5 1.5520 35.1 505 +8.5 0 R 41. 7 41. 7 4.1 12.5 1. 5687 35. 5 505 w R 35.1 49.1 3.5 12.3 1.5539 35.0 505 +5.1 :5 R 37. 8 45. 2 a. 8 13. 2 1. 5718 34. 7 R 43.5 39.2 4.3 13.0 1.5725 34.2 511 +8.1 1 R 34.4 48.3 3.5 13.8 1.5512 35.5 603 +8.0 2 R 30.3 54.5 3.0 12.1 1. 5512 35.5 501 +7.3 5

Having descnbed our mventwn what we clarm 1s: 3. The flmt glass of claim 2 in which the alkali car- 1. Substantially fluorine free flint glass with low index bonate is sodium carbonate. of refraction and high dispersion consisting essentially of a melt of a mixture of a metaphosphate of an alkaline References Cited in the file of thiipatent earth metal, an alkali carbonate and titanium oxide said UNITED STATES PATENTS titanium oxide comprising from 2.7% to 14.3% by weight of the melt and the metaphosphate comprising from m 2684304 Welssenberg et July 1954 47.6% to 54% by weight of the melt. OTHER REFERENCES 2. The flint glass of claim 1 in which the metaphos- The Glass Industry, Feb. 1935, p. 51, Article by B1511 phate is magnesium metaphosphate. and silverman. 

1. SUBSTANTIALLY FLUORINE FREE FLINT GLASS WITH LOW INDEX OF REFRACTION AND HIGH DISPERSION CONSISTING ESSENTIALLY OF A MELT OF A MIXTURE OF A METAPHOSPHATE OF AN ALKALINE EARTH METAL, AN ALKALI CARBONATE AND TITANIUM OXIDE SAID TITANIUM OXIDE COMPRISING FROM 2.7% TO 14.3% BY WEIGHT OF THE MELT AND THE METAPHOSPHATE COMPRISING FROM 47.6% TO 54% BY WEIGHT OF THE MELT. 